mode, the GPIO pins can handle 0-1.8 v.
Power and Reset Lines
POWER_ON_OFF_NOT, and RESIN_IN_NOT, each go through a Mosfet inverter
circuit to control the associated Huawei inputs as discussed in the Hardware Guide. The
input impedance is 122K or more, and the lines can be driven with logic that runs off
1.8v to 5 volts. A low input should be .6 volts or below and a high input should be 1.4
volts or above. You can find the Huawei Hardware Guide by going to
www.zoomtel.com/4575support
.
To power on the modem bring the POWER_ON_OFF_NOT pin high for 3-5 seconds
then back to low. This will cause the modem to power on.
To power off the modem bring the POWER_ON_OFF_NOT pin low for .5-1 seconds.
This will cause the modem to power off.
To reset the modem bring the RESIN_IN_NOT pin high for 50-100 milliseconds then
back to low. This will cause the modem to reset.
Sleep Mode Lines
WAKEUP_IN_NOT goes through a Mosfet inverter circuit to control the WAKEUP_IN
Huawei input as discussed in the Hardware Guide. The input impedance is 122K or
more, and it is driven with logic that runs off 1.8v to 5 volts. A low input should be .6 volts
or below and a high input should be 1.4 volts or above.
SLEEP_STATUS_NOT and WAKEUP_OUT_NOT are an open-drain output of a
N-channel Mosfet whose input is the associated Huawei output pin. Typically pull these
outputs up through a resistor to the plus supply of the logic connecting to this line.
To put the modem to sleep you must first pull the modem’s TXD pin high. This will force
the RXD pin at the Huawei module to go low. Next pull the WAKEUP_IN_NOT pin high
to put the modem to sleep. The modem will go to sleep. When in sleep mode, the RF
signal will take the modem out of sleep mode for 15-20 milliseconds every 1.25
seconds.
The SLEEP_STATUS_NOT pin will go low to indicate the modem is in sleep mode.
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